Carburetors have long been used to mix fuel and air for subsequent combustion in internal combustion engines. A chief advantage of such devices has been that they are, relatively speaking, uncomplicated, which allows them to be maintained and repaired without undue difficulty. In the recent past, however, a great many environmental regulations and laws have been enacted governing permissible exhaust and similar emissions from engines, particularly from automobile engines. This has necessitated the addition of extensive antipollution devices and controls, making engine systems, including their carburetion, extremely complicated, much more expensive, and very difficult to maintain and repair.
Even under normal conditions, an automobile engine is required to respond to a variety of demands, for example, operation under both cold and hot conditions; a need to accelerate rapidly, requiring rich fuel mixtures, and then to operate at less strenuous cruising speed conditions, permitting the use of leaner fuel mixtures, as well as almost infinite, constantly changing performance requirements between such extremes. Irrespective of the demands made on the engine, however, the engine system, including particularly the fuel system, must be capable of furnishing an extremely precise fuel mixture to the engine in order to meet the regulatory requirements and the combusion requirements imposed upon it.
In view of such needs, it has been recognized for some time that controlled fuel injection, particularly that of the electronic type, offers the best hope for meeting the often conflicting demands of fuel economy, high engine performance, and allowable emissions. Fuel injectors, on which electronically controlled fuel injection systems rely, consist of three basic parts, i.e., an electromagnet, a needle valve, and a nozzle. The electromagnet is activated, for example, by a signal from an electronic control unit which moves the injector's needle valve sufficiently away from the opening in the nozzle to allow the injector to deliver fuel in the form of a fine, atomized spray. The exact fuel required for any given operating condition can thus be introduced, based on information obtained from data delivered to the control unit from sensors located at multiple points throughout the engine and exhaust systems. The result is an extremely efficient method for controlling engine performance.
For the reasons described, fuel injector systems are the technology of choice for furnishing fuel to engines, and it is presently expected that virtually all domestically built automobile engines will be of the fuel injected type in the near future; with many of the injectors being of a type relying on some form of electronic injector control.
Notwithstanding their superior performance, however, fuel injectors are not without attendant problems. For example, they tend to accumulate unwanted deposits in the nozzle area, resulting in nozzle clogging which causes rough idling, as well as hesitation of the engine during acceleration. In this regard, injector nozzles are manufactured to extremely fine tolerances, and even microscopic foreign particles tend to result in their malfunction. Poor fuel quality, as well as ordinary operating conditions tend to be responsible for the unwanted accumulations of varnishes and other contaminants of the type described. These must be removed periodically if continued optimum performance of the injectors, and therefore of the engine is to be achieved.